British Telecom ESCORT, System Manual

Page: 29 / 36

5.2.13 Power fail
Failure of the mains supply will result in station
1
being connected to exchange line
1,
and station
4
being
connected to exchange line
2.
All other stations and
facilities will be inoperative. Calls in progress at
the time of failure may be lost, but no call will be
interrupted when power is restored.
6.
MAINTENANCE
All voltages and other parameters given in this section are given
as an indication of their expected values, these values are all
subject to a
5%
tolerance.
6.1 GENERAL
In order to restore customer service as q uickly as possible a
policy of maintenance changeout should be adopted. Neither the
CCU or the key module require any routine maintenance and on site
maintenance will be limited to changing the the fuse in the CCU.
6.2 TEST CONDITIONS
Exchange line Ports. The exchange line interface
incorporates components to enable it to test as a normal
DEL. Because the circuit contains volta g e dependent
resistors for protection it will test low loop if tested
with a megger.
Extension Ports. In the idle state i.e. no calls in
progress and all extensions on hook, the extensions are
connected to the intercom path, and a voltage of about
42
volts should be measured across the speech pair. No voltage
should be measured between the terminals "C" and "E"(LED
signals). Approximately 21 volts should be indicated
between terminals "C" and "D"(key signals).
6.3 FAULT LOCATION AND RECTIFICATION
The following table will assist fault location down to major sub­
system level. Faults proved to any subsystem of the CCU or to
the key module should result in the faulty unit being changed.
When using the table the possible faults and actions should be
considered in the order given.
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